PROJECT ABSTRACT HIV disproportionately affects sexual and gender minorities such as men who have sex with men (MSM) and transgender women (TGW). These individuals do not always receive the most up-to-date information on rapidly evolving guidelines in a time of new prevention technologies such as pre-exposure prophylaxis, leading to confusion in the face of recent HIV prevention developments. A lack of engagement in the traditional health care system also leads to infrequent testing for HIV. Novel ways are urgently needed to supply MSM and TGW with the most recent and accurate HIV prevention information to promote HIV health literacy and highlight the pitfalls of indirect assessments of potential infectivity rather than trimestral testing as recommended by the CDC. Mobile technologies such as text messaging present a dynamic new way to improve access to critical prevention information and care for MSM and TGW, but better ways of adapting them to the unique needs of MSM and TGW are needed, and creative ways of keeping them engaged are critical. Given the growing recognition that even if people have all necessary information and are motivated, they commonly fail to show healthy behavior, this proposal employs novel insights from behavioral economics to provide frequent feedback and incentives to keep participants engaged and support them in their intention to remain HIV negative. This proposal entails a 3-phase mobile technology based and BE supported HIV prevention intervention ? called Mobile Technology and Incentives (MOTIVES) - to increase engagement with HIV prevention information and improve testing frequency. Formative Phase 1 includes 30 semi-structured interviews with MSM and TGW to finalize the planned intervention based on the insights from a preliminary study. Phase 2 will enroll 200 HIV- negative MSM and TGW in an 18-month, two-arm randomized controlled trial (RCT). Those in the intervention group will receive weekly text messages with HIV prevention information, and can win reward points for correctly answering weekly quizzes to keep them engaged and improve their retention of the HIV prevention information. Those who continue to test negative for HIV at least once every three months can enter a prize drawing to win prizes, with larger chances for those correctly answering the weekly quizzes. The control group will receive the same HIV prevention information but without the incentives. The primary outcomes include frequency of HIV testing and HIV prevention knowledge. Phase 3 includes 7 exit focus groups (with 5-8 participants per group) to evaluate areas for study improvement and estimate parameters for future scale up. The Specific Aims are to 1) develop MOTIVES and finalize the weekly text message information content and the types of incentives; 2) implement and evaluate the impact of MOTIVES; and 3) evaluate areas of improvement for MOTIVES through focus groups and estimate mission-critical design parameters with point and confidence interval estimates for a subsequent, fully-powered R01 application.